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Columbia
Columbia, also known as Nuna and Hudsonland, was one of Earth's ancient s. It was first proposed by and is thought to have existed approximately in the . proposed that the assembly of the supercontinent Columbia was completed by global-scale collisional events during 2.1–1.8 Ga. Columbia consisted of proto- s that made up the cores of the continents of , , , , , and possibly , , and as well. The evidence of Columbia's existence is based upon and data. Size and location Columbia is estimated to have been approximately from North to South at its broadest part. The eastern coast of was attached to western , with southern against western . In this era most of was rotated such that the western edge of modern-day lined up with eastern , forming a that extended into the southern edge of . Assembly Columbia was assembled along global-scale 2.1–1.8 Ga collisional and contained almost all of Earth's continental blocks. As summarized by : * The cratonic blocks in South America and West Africa were welded by the 2.1–2.0 Ga Transamazonian and Orogens; * the and cratons in southern Africa were collided along the c. 2.0 Ga ; * the cratonic blocks of Laurentia were sutured along the 1.9–1.8 Ga , , , , , , and ; * the , , , and in (Eastern Europe) were joined by the 1.9–1.8 Ga Kola–Karelia, Svecofennian, Volyn-Central Russian, and Pachelma Orogens; * the Anabar and Aldan Cratons in Siberia were connected by the 1.9–1.8 Ga Akitkan and Central Aldan Orogens; * the East Antarctica and an unknown continental block were joined by the Orogen; * the South and North Indian Blocks were amalgamated along the ; * and the Eastern and Western Blocks of the were welded together by the c. 1.85 Ga Trans-North China Orogen. Outgrowth Following its final assembly at c. 1.82 Ga, the supercontinent Columbia underwent long-lived (1.82–1.5 Ga), subduction-related growth via accretion at key continental margins, forming at 1.82–1.5 Ga a great magmatic accretionary belt along the present-day southern margin of North America, Greenland, and Baltica. It includes the 1.8–1.7 Ga Yavapai, Central Plains and Makkovikian Belts, 1.7–1.6 Ga Mazatzal and Labradorian Belts, 1.5–1.3 Ga St. Francois and , and 1.3–1.2 Ga Elzevirian Belt in North America; the 1.8–1.7 Ga Ketilidian Belt in Greenland; and the 1.8–1.7 Transscandinavian Igneous Belt, 1.7–1.6 Ga Kongsberggian-Gothian Belt, and 1.5–1.3 Ga Southwest Sweden Granitoid Belt in Baltica. Other cratonic blocks also underwent marginal outgrowth at about the same time. In South America, a 1.8–1.3 Ga accretionary zone occurs along the western margin of the Amazonia Craton, represented by the Rio Negro, Juruena, and Rondonian Belts. In Australia, 1.8–1.5 Ga accretionary magmatic belts, including the Arunta, Mount Isa, Georgetown, Coen, and Broken Hill Belts, occur surrounding the southern and eastern margins of the North Australia Craton and the eastern margin of the Gawler Craton. In China, a 1.8–1.4 Ga accretionary magmatic zone, called the (Group), extends along the southern margin of the North China Craton. Congo craton The Congo Craton and the are stable Archaean blocks that formed a coherent landmass until the opening of the South Atlantic Ocean during the break-up of Gondwana ( 2000–130 Ma). They stabilised during the and Eburnian orogeny and have been affected by a long series of orogens since resulting in similar sequences on both blocks. Congo–São Francisco experienced three (LIP) events at 1380–1370 Ma, 1505 Ma, and 1110 Ma. The relative position of Congo–São Francisco within the supercontinent can be reconstructed because these LIP events also affected other Precambrian continental blocks. Within Nuna the northern part of was located adjacent to western São Francisco. 1110 Ma dyke swarms in Angola are absent in Siberia but coincide with the Umkondo LIP on the and magmatic event in the in India, the in South America, and the in (although the latter was located far from the other continental blocks). A series of 1500 Ma dyke swarms also support the close relation between Congo–São Francisco and Siberia: Kuonamka in Siberia and Curaçá and Chapada Diamantina in São Francisco and Angola. These dyke swarms radiate from a centre located in what is now north-eastern Siberia. Magmatic events in Congo (Kunene) and Siberia (Chieress) at 1384 Ma also corroborate the closeness of these two continents during at least 120 million years. It is possible that the 1110 Ma LIP in Congo–São Francisco, Amazonia, and India was part of a much larger event that also involved West Africa and Kalahari (with a possible but unlikely link to the 1075 Ma Warakurna LIP in Australia). However, while the palaeo-latitudes of India and Kalahari are well constrained, those of Amazonia and Congo–São Francisco are not, making any plate tectonic reconstruction speculative. At the time for the formation of the supercontinent at 550 the Congo Craton formed the already amalgamated central African landmass. The southern and eastern margins (modern coordinates) of this landmass was made of the Angola-Kasai block and Tanzanian Craton. These proto-Congo blocks were deformed in the but later stabilised. Fragmentation Columbia began to fragment about 1.5–1.35 Ga, associated with continental rifting along the western margin of (Belt-Purcell Supergroup), eastern India (Mahanadi and the Godavari), southern margin of (Telemark Supergroup), southeastern margin of (Riphean aulacogens), northwestern margin of (Kalahari Copper Belt), and northern margin of (Zhaertai-Bayan Obo Belt). The fragmentation corresponded with widespread anorogenic magmatic activity, forming - - - (AMCG) suites in North America, Baltica, Amazonia, and North China, and continued until the final breakup of the supercontinent at about 1.3–1.2 Ga, marked by the emplacement of the 1.27 Ga and 1.24 Ga mafic dyke swarms in North America. Other s associated with extensional tectonics and the break-up of Columbia include the in and the in Australia. An area around in northern , has been suggested to consist of rocks that originally formed part of Nuna 1.7 billion years ago in what is now Northern Canada. Configuration In the initial configuration of Rogers and Santosh (2002), , , , , and attached parts of are placed adjacent to the western margin of , whereas , (Northern Europe), and are positioned adjacent to the northern margin of North America, and is placed against . In the same year (2002), Zhao et al. (2002) proposed an alternative configuration of Columbia, in which the fits of Baltica and Siberia with Laurentia and the fit of South America with West Africa are similar to those of the Rogers and Santosh (2002) configuration, whereas the fits of India, East Antarctica, South Africa, and Australia with Laurentia are similar to their corresponding fits in the configuration of . This continental configuration is based on the available geological reconstructions of 2.1–1.8 Ga orogens and related Archean cratonic blocks, especially on those reconstructions between South America vs West Africa, Western Australia vs South Africa, Laurentia vs Baltica, Siberia vs Laurentia, Laurentia vs Central Australia, East Antarctica vs Laurentia, and North China vs India. Of these reconstructions, the fits of Baltica and Siberia with Laurentia, South America with West Africa, and Southern Africa with Western Australia are also consistent with . The new configuration of the Columbia supercontinent was reconstructed by Guiting Hou (2008) based on the reconstruction of giant radiating s. The newer configuration of the Columbia (Nuna) has been suggested by Chaves and Rezende (2019) supported on available paleomagnetic data and fragments of 1.79-1.75 Ga large igneous provinces. Chaves and Rezende 2019 Fragments of 1.79-1.75 Ga Large Igneous Provinces in reconstructing Columbia (Nuna): a Statherian supercontinent-superplume coupling? References Category:Earth